2004 kx 250 2stroke AF conversion with 06 kx 450f

was the welder a new guy in high school shop? I know welds don't have to be pretty to be strong, but I would not ride that frame as is. Really hate to be negative with someones build, but rather that than you getting hurt possiby.

Was thinking the same thing. It looks like an amateur did the work & doesn't look like those welds would hold up good for mx use based on the pics.. I did some fab work for 19 yrs. in the automotive industry so I'm somewhat familiar. Sketchy to say the least..
OP - My advice would be to have the welding / fab work looked at by a competent professional welder.

YIKES! Those welds look scary. I would redo it.
When I did my AF frame mods I mock'd up everything, and put inserts in each tube being welded back together, then paid a 100% pro to do the welding. The guy has 30 years experience. He's done a tone of stuff in the bicycle industry, car industry and high tech. I wouldn't have done the welds myself

^^That is what a weld is suppose to look like with a consistent thick bead.

This is utterly disgusting.

And, utterly unsafe. I f**king kid you not.

This is the sort of shit that puts you in Hospital.

Do Not "braze them up".

Find a Real welder and get it all re-done. What the hell that butcher used, I do not know. Perhaps a gasless MIG welder. It surely couldn't have been with a decent TIG welder (the machine and the operator), the proper gas, proper preparation, and proper welding rod.

Cut the 'inserts' out, and make another pair. Cut to get to unsullied tubeing. With such inserts, Even with telescoping internal inserts, I'd also do reinforcement plates on the inside, with the welds only going up the length (inwards of the corners) of the tubing, not across them (they create stress raisers with the HAZE zone, if a frame is not to be heat treated) . and , probably some rosette welds for the telescoping inserts .

And for f**ks sake, make sure the tubing and plate you use is quality, at least 6061 T6 /T651. Not any old crap.

Cut / grind the weld that the 'Y' piece has been subjected to. By the looks of it, you'll have to take a lot of material out just to get something that can be welded, safely and properly. Probably you'll even have to lift it to get to some healthy down tube, that has not been effed up by those atrocities of welding. "Diamond' / 'Roundel' shaped plates would be wise to place across the then re-done joint at the very least at the front. I do such things with any of the AFs I've done, so as to not just be 'hanging' off of welds - and I've got over 40 years of TIG experience - and, because most aluminum down tubes are (much) thinner above their original weld points.

This all assuming you want a Safe, Presentable bike to ride, that you can be proud to ride and have out in public.

Also, make damned sure you try to achieve the same swingarm pivot to counter shaft center orientation. The distance from both centers may be dictated by the cases on the 2t, but you should always be able to get the correct height of it. Do not make it to make things suit the ancillaries - they can be sorted. Swingarm pivot and CS Center geometry is a major part of a bikes Suspension and handling.

I'm Not having a go at you - I certainly am having a go at the bloody butcher that did such disgusting, dangerous work. Hell, he couldn't even put the inserts in straight, and that only takes a few clamps.

Fix it.

Agreed Bearuno, this is not on any level acceptable for any use what so ever.

Whoa dude.. Im a welder and I can tell you that the bike will put you in hospital or worse.
That is the poorest attempt I have seen in a while.

Honestly looking at the original welds compared to these you think there ok?
Even with good welds I'd want to get the frame heat treated.

It is a good thing the first guy said it can't be square tubing, meaning he can't do it. Not really sure what he is talking about it. The clean up went well, but still would get it redone, you really don't want the frame letting go and putting you ass over tea kettle, then who knows what else. Do It right.